Port #[rustc_specialization_trait] to the new attribute system

compiler/rustc_attr_data_structures/src/attributes.rs

@@ -343,6 +343,9 @@ pub enum AttributeKind {
     /// Represents `#[rustc_skip_during_method_dispatch]`.
     SkipDuringMethodDispatch { array: bool, boxed_slice: bool, span: Span },
 
+    /// Represents `#[rustc_specialization_trait]`.
+    SpecializationTrait(Span),
+
     /// Represents `#[stable]`, `#[unstable]` and `#[rustc_allowed_through_unstable_modules]`.
     Stability {
         stability: Stability,

compiler/rustc_attr_data_structures/src/encode_cross_crate.rs

@@ -55,6 +55,7 @@ impl AttributeKind {
             RustcLayoutScalarValidRangeStart(..) => Yes,
             RustcObjectLifetimeDefault => No,
             SkipDuringMethodDispatch { .. } => No,
+            SpecializationTrait(..) => No,
             Stability { .. } => Yes,
             StdInternalSymbol(..) => No,
             TargetFeature(..) => No,

compiler/rustc_attr_parsing/src/attributes/traits.rs

@@ -89,3 +89,10 @@ impl<S: Stage> NoArgsAttributeParser<S> for TypeConstParser {
     const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
     const CREATE: fn(Span) -> AttributeKind = AttributeKind::TypeConst;
 }
+
+pub(crate) struct SpecializationTraitParser;
+impl<S: Stage> NoArgsAttributeParser<S> for SpecializationTraitParser {
+    const PATH: &[Symbol] = &[sym::rustc_specialization_trait];
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
+    const CREATE: fn(Span) -> AttributeKind = AttributeKind::SpecializationTrait;
+}

compiler/rustc_attr_parsing/src/context.rs

@@ -45,7 +45,7 @@ use crate::attributes::stability::{
 use crate::attributes::test_attrs::IgnoreParser;
 use crate::attributes::traits::{
     CoinductiveParser, ConstTraitParser, DenyExplicitImplParser, DoNotImplementViaObjectParser,
-    SkipDuringMethodDispatchParser, TypeConstParser,
+    SkipDuringMethodDispatchParser, SpecializationTraitParser, TypeConstParser,
 };
 use crate::attributes::transparency::TransparencyParser;
 use crate::attributes::{AttributeParser as _, Combine, Single, WithoutArgs};
@@ -167,6 +167,7 @@ attribute_parsers!(
         Single<WithoutArgs<NonExhaustiveParser>>,
         Single<WithoutArgs<PassByValueParser>>,
         Single<WithoutArgs<PubTransparentParser>>,
+        Single<WithoutArgs<SpecializationTraitParser>>,
         Single<WithoutArgs<StdInternalSymbolParser>>,
         Single<WithoutArgs<TrackCallerParser>>,
         Single<WithoutArgs<TypeConstParser>>,

compiler/rustc_hir_analysis/src/collect.rs

@@ -880,7 +880,7 @@ fn trait_def(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::TraitDef {
     let specialization_kind =
         if attrs.iter().any(|attr| attr.has_name(sym::rustc_unsafe_specialization_marker)) {
             ty::trait_def::TraitSpecializationKind::Marker
-        } else if attrs.iter().any(|attr| attr.has_name(sym::rustc_specialization_trait)) {
+        } else if find_attr!(attrs, AttributeKind::SpecializationTrait(_)) {
             ty::trait_def::TraitSpecializationKind::AlwaysApplicable
         } else {
             ty::trait_def::TraitSpecializationKind::None

compiler/rustc_parse/src/validate_attr.rs

@@ -287,6 +287,7 @@ pub fn check_builtin_meta_item(
                 | sym::rustc_do_not_implement_via_object
                 | sym::rustc_coinductive
                 | sym::const_trait
+                | sym::rustc_specialization_trait
                 | sym::type_const
                 | sym::repr
                 | sym::align

compiler/rustc_passes/src/check_attr.rs

@@ -125,7 +125,8 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                     | AttributeKind::Coinductive(attr_span)
                     | AttributeKind::ConstTrait(attr_span)
                     | AttributeKind::DenyExplicitImpl(attr_span)
-                    | AttributeKind::DoNotImplementViaObject(attr_span),
+                    | AttributeKind::DoNotImplementViaObject(attr_span)
+                    | AttributeKind::SpecializationTrait(attr_span),
                 ) => {
                     self.check_must_be_applied_to_trait(*attr_span, span, target);
                 }